Australia's dry south to become even drier, scientists say

Inga Ting

Southern Australia has been warned to brace for more dry winters as a new study links the drying trend of the past few decades to human-induced changes in the atmosphere.

The US study found that southern Australia is drying out because human activity has changed the concentrations of greenhouse gases and ozone in the atmosphere.

Projections in the study, published in online journal Nature Geoscience, suggest that autumn and winter rainfall in south-west Australia may drop by up to 40 per cent by the end of the century.

Dr Nerilie Abram from the college of physical and mathematical sciences at the Australian National University said the emerging consensus among researchers painted a “very worrying picture”.

“Increasing greenhouse gas levels, as well as ozone depletion, have shifted the climate belts southwards, causing southern parts of Australia to miss out on the winter rainfall that farmers rely on for their crops,” she said.

Dr Abram said the impact of westerly winds pulling in tighter around Antarctica would not only change rainfall patterns, but would also warm the oceans around the edges of Antarctica. This would cause the margins of the large ice sheets to melt, with “big implications” for the pace of sea-level rise.

In an accompanying article in Nature Geoscience, Professor David Karoly from the University of Melbourne wrote: "The study is one of the very few instances where regional rainfall changes have been linked to human-caused climate change."

He also wrote that the prospect of winter rainfall continuing to decline posed “increasing risks to sustainable water resources”.

The study by US scientists Thomas Delworth and Fanrong Zeng used new computer models to simulate rainfall patterns from the past century. It found that simulations which included human-induced variations in atmospheric greenhouse gases and ozone levels mimicked many aspects of the observed pattern of rainfall decline.